Slurry residence time enhancement system

ABSTRACT

A slurry residence time enhancement system for a chemical mechanical polishing apparatus having a base, a platen on the base, a polishing pad on the platen and a polishing head over the polishing pad is disclosed. The system includes at least one slurry distribution unit having a slurry distribution member for positioning on the polishing pad. In operation of the CMP apparatus, the slurry distribution member redirects polishing slurry on the polishing pad to the polishing head. The system may alternatively or additionally include a rim for upward extension from the base and a seal for insertion between the platen and the polishing pad adjacent to the rim.

FIELD OF THE INVENTION

The present invention relates to chemical mechanical polishers used forpolishing semiconductor wafers in the semiconductor fabricationindustry. More particularly, the present invention relates to a slurryconservation system for reducing waste of polishing slurry by increasingthe slurry utilization rate in a chemical mechanical polishing (CMP)apparatus.

BACKGROUND OF THE INVENTION

Apparatus for polishing thin, flat semiconductor wafers are well-knownin the art. Such apparatus normally includes a polishing head whichcarries a membrane for engaging and forcing a semiconductor waferagainst a wetted polishing surface, such as a polishing pad. Either thepad or the polishing head is rotated and oscillates the wafer over thepolishing surface. The polishing head is forced downwardly onto thepolishing surface by a pressurized air system or similar arrangement.The downward force pressing the polishing head against the polishingsurface can be adjusted as desired. The polishing head is typicallymounted on an elongated pivoting carrier arm, which can move thepressure head between several operative positions. In one operativeposition, the carrier arm positions a wafer mounted on the pressure headin contact with the polishing pad. In order to remove the wafer fromcontact with the polishing surface, the carrier arm is first pivotedupwardly to lift the pressure head and wafer from the polishing surface.The carrier arm is then pivoted laterally to move the pressure head andwafer carried by the pressure head to an auxiliary wafer processingstation. The auxiliary processing station may include, for example, astation for cleaning the wafer and/or polishing head, a wafer unloadstation, or a wafer load station.

More recently, chemical-mechanical polishing (CMP) apparatus has beenemployed in combination with a pneumatically-actuated polishing head.CMP apparatus is used primarily for polishing the front face or deviceside of a semiconductor wafer during the fabrication of semiconductordevices on the wafer. A wafer is “planarized” or smoothed one or moretimes during a fabrication process in order for the top surface of thewafer to be as flat as possible. A wafer is polished by being placed ona carrier and pressed face down onto a polishing pad covered with aslurry of colloidal silica or alumina in deionized water.

In current CMP apparatuses, about 90% of the polishing slurry is notutilized to polish wafers, and therefore, is wasted. Accordingly, aslurry residence time enhancement system is needed for reducing waste ofpolishing slurry by increasing the slurry utilization rate in a chemicalmechanical polishing (CMP) apparatus.

SUMMARY OF THE INVENTION

The present invention is generally directed to a slurry residence timeenhancement system for a chemical mechanical polishing apparatus havinga base, a platen on the base, a polishing pad on the platen and apolishing head over the polishing pad. The system includes at least oneslurry distribution unit having a slurry distribution member forpositioning on the polishing pad. In operation of the CMP apparatus, theslurry distribution member redirects polishing slurry on the polishingpad to the polishing head. The system may alternatively or additionallyinclude a rim for upward extension from the base and a seal forinsertion between the platen and the polishing pad adjacent to the rim.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is a perspective view of an illustrative embodiment of the slurryresidence time enhancement system according to the present invention;

FIG. 2 is a perspective view of a slurry distributor of the slurryresidence time enhancement system;

FIGS. 3A-3D are schematic views of a chemical mechanical polishing (CMP)apparatus, in implementation of the slurry residence time enhancementsystem according to the present invention; and

FIG. 4 is a perspective sectional view of a CMP apparatus, illustratinga seal between the polishing pad and rim of the apparatus.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, an illustrative embodiment of the slurryresidence time enhancement system, hereinafter system, according to thepresent invention is generally indicated by reference numeral 10. Thesystem 10 is shown in conjunction with a rotary-type chemical mechanicalpolishing (CMP) apparatus 12, which may be conventional. The CMPapparatus 12 includes a circular base 14. A platen 17 is mounted forrotation on the base 14, and a motor (not shown) which is typicallyprovided in the base 14 engages and rotates the platen 17 in operationof the CMP apparatus 10. A polishing pad 18 is supported by the platen17. A polishing head 24 is supported over the polishing pad 18 forholding and pressing a wafer (not shown) against the polishing pad 18 asthe polishing pad 18 is rotated by the platen 17. A slurry delivery arm26 (FIGS. 3A-3D), having a pair of nozzles 26 a, is extendible over thepolishing pad 18 to dispense a polishing slurry 28 onto the polishingpad 18 during polishing of a wafer (not shown) mounted on the bottom ofthe polishing head 24.

As shown in FIG. 1, the slurry residence time enhancement system 10includes at least one, and preferably, a pair of slurry distributionunits 30 which are provided in conjunction with the CMP apparatus 12. Asshown in FIG. 2, each slurry distribution unit 30 typically includes abase 32 from which extends a support conduit 34. An arm tee 36 includesa vertical segment 38 which is inserted and secured in the supportconduit 34 typically using multiple fasteners and a horizontal segment40 which extends generally perpendicularly from the vertical segment 38.A support arm 42 extends generally horizontally from the horizontalsegment 40.

A slurry distribution member 48 is mounted on the support arm 42.Accordingly, a sleeve 44 is provided on the extending end of the supportarm 42, and an insert 46, to which is mounted the slurry distributionmember 48, extends into the sleeve 44. The insert 46 is mounted in thesleeve 44 typically using multiple fasteners (not shown) or othersuitable technique. The slurry distribution member 48 typically includesa generally elongated, arcuate or semicircular upper segment 52, fromwhich the insert 46 extends, and a generally elongated, arcuate orsemicircular lower segment 50 which is secured to the upper segment 52typically using multiple fasteners 54 or alternative technique. Atapered end portion 51 terminates each end of the lower segment 51. Eachslurry distribution member 48 includes a concave side 49 a and a convexside 49 b and typically has a curvature equal to that of a circle havinga diameter of about 12 inches.

As shown in FIG. 1, the slurry residence time enhancement system 10includes at least one, and preferably, a pair of the slurry distributionunits 30, each of which is positioned adjacent to the base 14 of the CMPapparatus 12. The support arm 42 extends over the rim 16 and thepolishing pad 18 of the CMP apparatus 12. The slurry distribution member48, suspended from the support arm 42, contacts the polishing pad 18. Asshown in FIG. 3A, the concave side 49 a of each slurry distributionmember 48 is oriented against the direction of rotation, and the convexside 49 b of each slurry distribution member 48 is oriented with thedirection of rotation, of the polishing pad 18 during polishing of awafer on the polishing polishing head 24. As shown in FIG. 4, the slurryresidence time enhancement system 10 may further include a rim 16 whichextends upwardly from the base 14, around the circumference of the base14, and a liquid-tight seal 20 which is provided between the platen 17and the polishing pad 18, adjacent to the rim 16. Preferably, the rim 16has a height of at least about 6 mm and the seal 20 has a width of atleast about 0.5 mm and may be offset with respect to the base 14, asfurther shown in FIG. 4.

Referring next to FIGS. 3A-3D, in typical use of the slurry residencetime enhancement system 10, the CMP apparatus 12 is operated typicallyin the conventional fashion. Accordingly, a wafer (not shown) is mountedon the bottom surface of the polishing head 24. As the polishing slurry28 is dispensed from the nozzles 26 a of the slurry dispensing arm 26,onto the polishing pad 18, as shown in FIG. 3A, the polishing pad 18 andthe polishing head 24 are rotated typically in the counterclockwisedirection, as indicated by the arrows.

As it rotates, the polishing head 24 presses the wafer against thepolishing pad 18. Simultaneously, as shown in FIG. 3B, the polishingslurry 28 on the polishing pad 18 contacts the wafer on the polishinghead 24 and facilitates polishing of the wafer. The polishing slurry 28may be continually dispensed from the slurry delivery arm 26 to ensureadequate contact of the polishing slurry with the rotating waferthroughout the chemical mechanical polishing operation. Consequently,were it not for the presence of the slurry distribution members 48, thepolishing slurry 28 would have a tendency to gradually accumulate at theedge of the polishing pad 18, as shown in FIG. 3C, due to centrifugalforce. However, the polishing pad 18 rotates the polishing slurry 28into contact with the concave surface 49 a of each slurry distributionmember 48, causing the polishing slurry 28 to accumulate in the concavesurface 49 a of the slurry distribution member 48, as shown in FIG. 3D.Furthermore, the slurry distribution members 48 redistribute or redirectthe accumulated polishing slurry 28 to the polishing head 24 and ensurecontinued polishing of the wafer without requiring the dispensing ofadditional polishing slurry 28 from the slurry dispensing arm 26 andonto the polishing pad 18. This increases the utilization rate of thepolishing slurry 28 by increasing the residence time of the polishingslurry 28 on the polishing pad 18, thereby preventing wasting of thepolishing slurry 28 throughout the chemical mechanical polishingoperation. Also, the seal 20 prevents the polishing slurry 28 fromrotating off of the platen 17 due to the centrifugal force acting on thepolishing slurry 28 as it is rotated on the polishing pad 18.

While the preferred embodiments of the invention have been described, itwill be recognized and understood that various modifications can be madein the invention and the appended claims are intended to cover all suchmodifications which may fall within the spirit and scope of theinvention.

1. A slurry residence time enhancement system for a chemical mechanicalpolishing apparatus having a base, a platen on the base, a polishing padon the platen and a polishing head over the polishing pad, comprising:at least one slurry distribution unit having a slurry distributionmember for positioning on said polishing pad and redirecting polishingslurry on said polishing pad to said polishing heads; wherein saidslurry distribution member comprises a generally semicircularconfiguration with a concave side, said concave side oriented against adirection of rotation of said polishing pad.
 2. The slurry residencetime enhancement system of claim 1 wherein said at least one slurrydistribution unit comprises a pair of slurry distribution units. 3.(canceled)
 4. The slurry residence time enhancement system of claim 1wherein said slurry distribution member corresponds to a curvature of acircle having a diameter of about 12 inches.
 5. The slurry residencetime enhancement system of claim 1 wherein said slurry distributionmember comprises an upper segment and a lower segment carried by saidupper segment.
 6. The slurry residence time enhancement system of claim5 wherein said lower segment has tapered ends.
 7. The slurry residencetime enhancement system of claim 1 wherein said at least one slurrydistribution unit comprises a base and a support arm carried by saidbase, and wherein said slurry distribution member is carried by saidsupport arm.
 8. The slurry residence time enhancement system of claim 7wherein said slurry distribution member comprises a generallysemicircular upper segment carried by said support arm and a generallysemicircular lower segment carried by said upper segment.
 9. A slurryresidence time enhancement system for a chemical mechanical polishingapparatus having a base, a platen on the base, a polishing pad on theplaten and a polishing head over the polishing pad, comprising: a slurrydistribution member comprising a generally semicircular configurationwith a concave side, said concave side oriented against a direction ofrotation of said platen and said polishing pad; a rim extending upwardfrom the base around the circumference of the base; and a seal betweenthe platen and the polishing pad adjacent to said rim.
 10. The slurryresidence time enhancement system of claim 9 wherein said rim has aheight of at least about 6 mm.
 11. The slurry residence time enhancementsystem of claim 9 wherein said seal has a width of at least about 0.5mm.
 12. The slurry residence time enhancement system of claim 9 whereinsaid rim is offset with respect to said base.
 13. A slurry residencetime enhancement system for a chemical mechanical polishing apparatushaving a base, a platen on the base, a polishing pad on the platen and apolishing head over the polishing pad, comprising: at least one slurrydistribution unit having a slurry distribution member for positioning onthe polishing pad and redirecting polishing slurry on the polishing padto the polishing head; a slurry delivery arm positioned over saidpolishing pad for dispensing slurry on said polishing pad; a rimextending upward from the base around the circumference of the base; anda seal for insertion between the platen and the polishing pad adjacentto said rim; wherein said slurry distribution member comprises agenerally semicircular configuration with a concave side, said concaveside oriented against a direction of rotation of said polishing pad andpositioned in said direction of rotation between said slurry deliveryarm and said polishing head.
 14. The slurry residence time enhancementsystem of claim 13 wherein said at least one slurry distribution unitcomprises a pair of slurry distribution units.
 15. (canceled)
 16. Theslurry residence time enhancement system of claim 13 wherein said atleast one slurry distribution unit comprises a base and a support armcarried by said base, and wherein said slurry distribution member iscarried by said support arm.
 17. The slurry residence time enhancementsystem of claim 13 wherein said slurry distribution member comprises agenerally semicircular upper segment carried by said support arm and agenerally semicircular lower segment carried by said upper segment. 18.The slurry distribution time enhancement system of claim 17 wherein saidlower segment has tapered ends.
 19. The slurry residence timeenhancement system of claim 13 wherein said rim has a height of at leastabout 6 mm.
 20. The slurry residence time enhancement system of claim 13wherein said seal has a width of at least about 0.5 mm.
 21. The slurryresidence time enhancement system of claim 1, further comprising aslurry delivery arm positioned over said polishing pad for dispensingsaid slurry on said polishing pad wherein said at least one slurrydistribution unit is positioned between said slurry delivery arm andsaid polishing head in said direction of rotation.
 22. The slurryresidence time enhancement system of claim 1, wherein said slurrydistribution member is positioned adjacent an said polishing pad edge tointercept and redirect said slurry from said polishing pad edge towardsaid polishing head.